1. Field of the Invention
The present invention relates to an image scanner and, more specifically, to an improvement of a scanner structured such that an object such as an original is fixedly placed and scanned by moving a scanner including an illuminating light source, a photodetector and the like to provide image information of the object.
2. Description of the Background Art
There has been a strong demand of treating image information in the same manner as in treating document information in various fields including the field of office automation. A scanner is one of the apparatuses provided to meet such a demand. The scanner is structured such that an object such as an original is illuminated by light from an illuminating light source and the light reflected from the object is detected by a one dimensional image sensor comprising CCDs (Charge Coupled Devices) to provide image information of the object. One type of such scanner is called a self-running type scanner in which an object such as an original is fixedly placed and a scanner portion is moved for scanning the object by using the light from the illuminating light source.
FIG. 1 schematically shows a whole structure of a conventional self-running type scanner. Referring to FIG. 1, the conventional self-running type scanner comprises a scanner unit 1 for illuminating an object such as an original (not shown) with light having a prescribed wavelength and for detecting light reflected from the object to provide image information of the object, and a driving portion 2 for driving running of the scanner unit 1. The scanner unit 1 responds through a wire 3 to the rotation of a pulse motor 4 included in the driving portion 2, to be moved along the Y direction. The rotation of the pulse motor 4 included in the driving portion 2 is transmitted to the wire 3 through a pulley 5b. A pulley 5a is similarly provided at another portion of the wire 3 so as to smoothly move the scanner unit 1 along the Y ,direction. As the scanner unit 1 runs in the Y direction, the illuminating light from the illuminating light source included in the scanner unit 1 illuminates an object such as an original (hereinafter simply referred to as an object) while scanning the same, so that the desired image information of the object can be provided.
The scanner unit 1 and the driving portion 2 are contained in a scanner body 6. A scanner upper lid 7 is provided on the scanner body 6 for sealing the scanner unit 1, the driving portion 2 and so on, so as to prevent contamination due to dust and the like from outside.
A plate 8 formed of a transparent material for transmitting the illuminating light from the illuminating light source included in the scanner unit 1 and the light reflected from the object is provided at a prescribed region of the scanner body 6. The plate 8 is formed of a material such as acryl, glass or the like which is transparent to the illuminating light from the illuminating light source therethrough.
In addition, a white balance sheet 9 for providing a white level reference of the light reflected from the object is provided at a prescribed position of the scanner body 6. The scanner unit 1 scans the white balance sheet 9 to detect the light reflected from the white balance sheet 9. The detected level of the reflected light is used as the reference level to the white level of the light reflected from the, object during scanning. This is a measure to prevent an erroneous reading caused by a change in intensity of the reflected light associated with changes of the environment such as a change in intensity of the illuminating light from the light source.
FIG. 2 schematically shows an internal structure of the scanner unit shown in FIG. 1. Referring to FIG. 2, the scanner unit comprises an illuminating light source 10 for illuminating an object, reflecting mirrors 11a, 11b, 11c and 11d reflecting the light reflected from the object (including the white balance sheet) and providing an optical path of the reflected light, and a lens 12 for receiving and focusing the reflected light from the reflecting mirror 11d onto a one dimensional image sensor 13 consisting of, for example, CCDs (Charge Coupled Devices). The one dimensional image sensor 13 converts the applied optical signals into electric signals to transmit the same to an image information processing apparatus through a path, not shown.
In the above described structure, when the scanner unit 1 scans the object along the Y direction, the scanning of the object in the X direction is carried out by the one dimensional image sensor 13. In such a self-running type scanner, the object is fixedly placed and illuminated by the light from the illuminating light source 10 and the illuminating light from the object is reflected by the reflecting mirrors 11a through 11d to be introduced to the one dimensional image sensor 13 through the lens 12 for image formation, so that the object can be scanned in both X and Y directions, providing desired image information of the object.
In the above described structure of the conventional self-running type scanner, the scanner unit 1 and the driving portion 2 for driving the running of the scanner unit 1 are separately provided, and the scanner unit 1, the driving portion 2 and the scanner driving wire 3 must be contained in a scanner body 6. In addition, the scanner body and the scanner upper lid are both of a separate type structure, so that the number of components of the units constituting the conventional self-running type scanner becomes large and the apparatus itself becomes complicated, preventing reduction in size of the apparatus. Since the apparatus comprises a large number of parts, it takes much time to assemble the self-running type scanner. The larger number of parts and the long time required for the assembly prevent provision of an inexpensive self-running type scanner.
A structure of a scanner unit having a rotary motor attached integrally thereto is disclosed in Japanese Patent Laying Open No. 61-232764. In this prior art, a flanged roller which is in contact with a guiding slide rod is arranged at a tip end portion of an output axis of the rotary motor, and a fixed axis having a V grooved bearing in contact with another slide rod is provided at a tip end of the other end of the unit. The scanner unit moves along the slide rods by the rotation of the output axis of the rotary motor.
A self-scanning type (self-running type) copying apparatus in which an original reading mechanism is moved by rotating a driving roller by means of a microstep motor is disclosed in Japanese Patent Laying Open No. 58-111476. In this copying apparatus, feeding of recording paper and the scanning of the original are both carried out by the driving of the same step motor. No guiding means for moving the copying apparatus is provided in this prior art.